The invention relates to a coupling between the rotor of a belt tensioner rotary drive and a drive shaft.
A coupling of this kind is known from German utility model 295 15 703.8. The drive shaft coupled to the belt reel of a belt retractor carries an externally toothed coupling wheel, into the toothing of which two coupling pawls swivel-mounted on the rotor are engageable. The coupling pawls are configured crowned at their end opposite the pawl tip and are supported over a large surface area by a correspondingly concavely shaped supporting surface area in a pocket bearing on the rotor to distribute the extremely high loads occurring in the coupling process both radially and circumferentially to a large supporting surface area.
The invention has the purpose of sophisticating this known coupling to the effect that the coupling process is accelerated and is already concluded when rotation of the rotor commences. In accordance with the invention the coupling pawl is toggle-mounted on a knife-edge bearing on the rotor. The invention is based on the idea that the large surface area contact between the coupling pawl and the supporting surface area which is favorable to distributing the load in the coupling process results in increased friction which delays the coupling process. When mounting the coupling pawl on a knife-edge bearing the friction is negligible so that no delay occurs in the coupling process. Despite mounting the coupling pawl on a knife-edge bearing, distribution of the loads over a large supporting surface area is lastly achieved. For one thing, namely, the coupling pawl, once having attained its engagement position, is able to contact the supporting surface over a large surface area. For another thing, the knife-edge bearing formed more particularly by a pointed protuberance may be deformed under load so that the pawl comes into contact with the supporting surface area by its side facing away from the pawl tip. The plastic deformation in the region of the knife-edge bearing is a desired effect by which the movement of the coupling pawl in contacting the toothing of the coupling wheel is damped. In the preferred embodiment this damping effect is enhanced by a plurality of additional deformation elements at the supporting surface area.